The present invention generally relates to hand held power tools and more particularly to routers.
Craftsmen and artisans have been using routers for decades to perform many woodworking tasks, including cutting decorative shapes and edges in wood and other suitable materials. While fixed base routers, i.e., ones where the housing is fixed or locked in a position relative to the base after the depth of cut of the tool bit has been set, are often used by professional artisans, many router users prefer plunge type routers which have a housing that is rapidly movable relative to a base with the amount of vertical movement being determined by a depth limiting mechanism.
Plunge routers generally have a housing in which a motor is located, although in certain types of routers a removable motor assembly may be carried by a housing. In this type of situation, generally known in the art as a hybrid router, the motor assembly can be removed from the housing and placed in a fixed base housing so that it can be operated in that manner. If the motor assembly is mounted into a plunge type router housing or if the router is a dedicated plunge-type router, the housing is generally mounted on a base structure of the type that typically has a pair of spaced vertical guide posts along which the housing can be vertically moved. During use, an artisan may press down on the housing, typically by pressing down on handles that extend from opposite sides of the housing or motor assembly so that as the housing is pressed downwardly toward the base structure, the router bit penetrates into a work piece that is to be cut.
An adjustable depth of cut mechanism is nearly always provided to control the depth in which the router bit can penetrate the work piece to produce the desired cutting operation. Generally, when the artisan presses down on the handles to have the router bit penetrate the work piece, a handle or lever mechanism can be set to hold the router at the desired position during use. When the router bit is to be removed from the work piece, the lever can be released and springs located in the router around the posts act to push the housing upwardly away from the base structure. Typically, the springs are coil springs that surround each of the posts and bear against the base structure as well as the housing and provide a biasing force tending to separate the two components. It is also typical for the springs to be housed in generally cylindrical or oblong accordion-like baffles that hide the springs from view and to provide a barrier for dust and other debris from coming into contact with the post surface and the interface between the post and openings in the housing in which sliding movement of the housing on the post occurs.
Because there are two posts on which the housing must slide, it is not unusual for a particular router design to exhibit a tendency for the housing to bind during sliding movement and one of the solutions to minimize such binding is to have a single spring on one of the posts or to have springs on both posts with the spring force of one of the springs being greater than the other.